Fluid systems found in heaters, air conditioners, coolers, dehumidifiers, freezers and the like utilize a number of complex components which serve as fluid conduit. For example, a trunk or header tube may be required to interconnect with a number of lateral tubes of smaller diameter such as the hairpin-bent tubes of a fin-tube evaporator or condenser. A number of techniques can be used for joining the hairpin tubes to the header tube but the most desirable connection method involves the formation of a stub tube or lateral extension at each of several spaced intervals along the header tube. The problem with the prior art is to form an extension or stub tube of substantial length so as to facilitate the production of a secure connection to the hairpin tubes.